Fine metal mask (FMM) technology is a method of evaporating a light-emitting material corresponding to each of pixels in an OLED (organic light-emitting display) device onto an array substrate of LTPS (low temperature poly silicon) type by an evaporation method according to a corresponding process. Red, green or blue light-emitting layer is evaporated to a corresponding pixel area by using a pattern (for example, a plurality of square-shaped slits or a plurality of strip-shaped slits) on a FMM sheet of the FMM.
As illustrated in FIG. 1 and FIG. 2, in the known FMM design, a cover in a longitudinal direction and a howling (not illustrated in the figure) in a horizontal direction for supporting the FMM sheet with a certain pattern are designed as a structure with greater width in the middle and smaller width at both ends, so as to reduce a width of a groove on a frame of the FMM for accommodating the supporting structure, thereby increasing a welding area (as illustrated in FIG. 1, denoted by reference numeral “a”) between the FMM sheet and the frame, and ensuring a welding stability of the FMM sheet.
However, when both ends of the cover or the howling are welded into the groove of the frame, the cover or the howling needs to be stretched to a certain extent to be in a tension state during a welding process, and both sides of a middle portion with relatively greater width of the cover or the howling would be curled downward, which may affect the stability of the supporting structure for supporting the FMM sheet, and hence affect an evaporated pattern of the OLED product.